Barlow - before or after diagonal?

[yagon]

Can a barlow be used before and after a diagonal?

How does this affect the image?

[janoskiss (Steve H)]

after. if you can reach focus before, then you'll get more magnification than the barlow specifies.

[Robert_T]

Hi Yagon - As Steve says if you use the diagonal after the barlow it will increase you magnification. This can be useful though, especially for planetary imaging when it functions like an extension tube for increased image scale.

If you want the barlow to perform to the amplification specified you'll need to put in at the end of the optical train.

cheers,

[Rastis]

Does this mean you could put a spacer between the eyepiece and the Barlow on a newtonian to gain more magnification. To use my Meade#140 barlow it needs to be pulled out of the focusser about half an inch. With a spacer could I push the barlow right in and space the eyepice out.
Rastis.

[janoskiss (Steve H)]

Yes. But the image quality will suffer if you add too much length. You can also reduce the magnification with a recessed adapter (applicable to 2" long barlows only).

[Rastis]

Would it turn it from a two times barlow to say a three times. With a 9mm eyepiece the magnification still won't be extreme. It would be easy enough for me to make a extension tube.

[bird (Anthony Wesley)]

The effect depends on the specific barlow - for some barlows the magnification will *decrease* if you move the eyepiece further away on the output side. e.g. the TV 4x powermate does this.

You should check the specs from the manufacturer if you can, or if it's easier just try it and see what happens.

Bird

[asimov (John)]

Yes Rastis, the meade APO #140 will work that way. I have the same barlow & use an extension tube as well to gain more image scale. Bear in mind I don't use this setup for visual, only imaging.